Electric traction system for a railway vehicle and protection method realized by such a system

Abstract

A system includes a converter for powering a synchronous electric machine to which it is connected by cables, an insulating device and a mechanism for short-circuiting phases of the machine. The system includes primary detectors for detecting an overcurrent in the converter and a securing device able to open the insulating device when receiving a primary detection signal emitted by the primary detector. The system also includes secondary detectors able to detect a short-circuit downstream from the insulating device and to emit a secondary detection signal toward the securing device, the latter actuating the closing of the mechanism for short-circuiting as long as they have already received a primary detection signal having led to the opening of the insulating device.

What is claimed is: 
     
       1. An electric traction system for a railway vehicle, comprising:
 a synchronous electric traction machine having a plurality of phases; and, 
 a power supply circuit, the power supply circuit including a converter, connected to a DC voltage source and delivering a polyphase voltage adapted to power the synchronous electric traction machine to which the converter is connected by a plurality of electric cables, an insulator and an electrical connector configured to be capable of short-circuiting the phases of the synchronous electric traction machines, placed downstream from the insulator, 
 the synchronous electric traction machine further comprising a converter control, a primary detector for detecting an over-current in a plurality of output branches of the converter, and an actuator configured to actuate an opening of the insulator upon reception of a primary detection signal emitted by the primary detector, 
 wherein the electric traction system further includes a secondary detector for detecting a fault of a short-circuit type downstream from the insulator and emitting a secondary detection signal toward the actuator, 
 and wherein the actuator actuates a closing of the electrical connector for short-circuiting the phases of the synchronous electric traction machine upon reception of the secondary detection signal, on the condition the actuator has already received the primary detection signal emitted by the primary detector and having led to actuating the opening of the insulator 
 wherein the secondary detector include at least one temperature sensor, for measuring a temperature corresponding to an internal temperature of the synchronous electric traction machine. 
 
     
     
       2. The system according to  claim 1 , wherein the secondary detector includes a secondary detection device for calculating a time variation of the temperature measured by the or each temperature sensor. 
     
     
       3. The system according to  claim 2 , wherein the secondary detection device compares the time variation of the temperature to a predetermined threshold, and emits a short-circuit detection signal when the time variation of the temperature is above said predetermined threshold. 
     
     
       4. The system according to  claim 3 , wherein the predetermined threshold is greater than +1.0° C./s. 
     
     
       5. The system according to  claim 1 , wherein the secondary detector discriminates whether the over-current detected by the primary detector is a non-dead short-circuit external to the synchronous electric traction machine of the initiating type between the electric cables, by comparing a time variation of the temperature to a second predetermined threshold. 
     
     
       6. A securing method implemented in an electric traction system for a railway vehicle, comprising:
 a synchronous electric traction machine having a plurality of phases; and, 
 a power supply circuit, the power supply circuit including a converter, connected to a DC voltage source and delivering a polyphase voltage adapted to power the synchronous electric traction machine to which the converter is connected by a plurality of electric cables, an insulator and an electrical connector configured to be capable of short-circuiting the phases of the synchronous electric traction machines, placed downstream from the insulator, 
 the synchronous electric traction machine further comprising a converter control, a primary detector for detecting an over-current in a plurality of output branches of the converter, and an actuator configured to actuate an opening of the insulator upon reception of a primary detection signal emitted by the primary detector, 
 wherein the electric traction system further includes a secondary detector for detecting a fault of a short-circuit type downstream from the insulator and emitting a secondary detection signal toward the actuator, 
 and wherein the actuator actuates a closing of the electrical connector for short-circuiting the phases of the synchronous electric traction machine upon reception of the secondary detection signal, on the condition the actuator has already received the primary detection signal emitted by the primary detector and having led to actuating the opening of the insulator 
 wherein the secondary detector include at least one temperature sensor, for measuring a temperature corresponding to an internal temperature of the synchronous electric traction machine, 
 wherein the securing method includes the steps successively consisting of: 
 detecting an overvoltage in at least one output branch of the converter; 
 actuating the opening of the insulator; 
 then detecting a fault of the short-circuit type downstream from the insulator; and, in the affirmative, 
 actuating the closing of the electrical connector for short-circuiting the phases of the synchronous electric traction machine.